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Anatomy: Diagram of a Neuron
An understanding of brain anatomy is the next important component of learning how the addiction process occurs. The brain is made up of millions of nerve cells, or neurons. Neurons act as the body's communication system. Neurons are made up of four basic parts, (a) the cell body, or soma, (b) dendrites, (c) axon, or nerve fiber, and (d) axon terminal (Figure 1).
Figure 1
The cell body and dendrite are primarily responsible for receiving messages from other neurons. The axon is the transmitter, taking messages away from the cell body. This message transfer from the axon of one nerve cell to the dendrite of another nerve cell is called neurotransmission. When action potentials reach axon terminals neurotransmitters are released. Neurotransmitters are a chemical messenger of neurologic information that is released from a nerve cell, which thereby transmits an impulse from a nerve cell to another nerve, muscle, organ, or other tissue. Next, neurotransmitters diffuse across the synaptic cleft to bind with specific receptors on the dendrite of the 'message receiving' neuron.
The neurotransmitter stimulates or inhibits an electrical response in the receiving neuron. It is important to appreciate that it is the receptor that dictates the neurotransmitter's effect.
Figure 2. Neurotransmission (NIDA, 2006) 6
More than 40 neurotransmitters have been identified. Psychoactive drugs change neurotransmission. Table 3 lists several neurotransmitters, their function and the drugs that affect them.
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Neuron
